json.nl=map - NamedList is represented as a JSON object. Although this is the simplest mapping, a NamedList can have optional keys, repeated keys, and preserves order. Using a JSON object (essentially a map or hash) for a NamedList results in the loss of some information.

json.nl=arrarr - represent a NamedList as an array of two element arrays [[name1,val1], [name2, val2], [name3,val3]]